(1) The Field of the Invention
The present invention relates to a pressurized air operated nailing or stapling device and, more particularly, to a mechanism designed for sequentially driving into wooden workpieces (such as pieces of furniture, for example) large headed staples. The mechanism comprises a pressurized air operated cylinder and a reciprocating piston connected to a driver hammer rod which operates into a guide passage. An elongate staple magazine is provided with a plurality of large headed staples which is positioned prior to service. The individual staples are sequentially moved into the said guide passage.
The device of the invention is generally designed for sequentially driving large headed nails such as tacks (e.g., of the type having a large dome-shaped head and a relatively short stem) adapted for nailing upholstery to pieces of furniture. More particularly the device is designed for sequentially driving staple-type nails each having a relatively large dome-shaped head and two parallel stems or shanks integrally connected to said head at two diametrally opposite portions thereof.
(2) The Prior Art
The automatic nailing and stapling devices are well known in the art. The supply of nails or staples to be automatically and sequentially driven is generally located into an elongated straight magazine or in a cartridge. Said magazine comprises a pair of supporting surfaces for slidably supporting the opposite portions of the nail or staple heads, and a center groove along which the shanks are aligned.
A relatively great number of simple U-shaped staples (such as those used for stapling papers together can be slidably received in a rather short magazine. The plurality of staples is biased generally by spring means along the magazine towards the guide passage for individually driving the staples one after another.
On the other hand, if large headed nails or staples are to be supplied for sequential driving, several problems have been heretofore presented. The diametral dimension of the staple heads causes provision of a substantially long magazine for accommodating therein an adequate number of staples for use between any re-loading operations. This feature leads to provision of a non-straight magazine. The nailing or stapling machines of the type are considered generally portable tools and must be adapted for use in different positions and directions. Therefore the weight or gravity cannot be relied upon for providing the regular progress of the staples along the magazine towards the operational location. According to a known arrangement (see U.S. Pat. No. 3,826,419), the supply comprises a string of ribbon-connected nails or staples which can be step-by-step pulled (instead of being pushed) towards the driving location by means of an index pawl or other suitable feed claw mechanisms acting on the nail or staple which is adjacent (or very near) to the guide passage in which the driver hammer operates. Such arrangement has, several shortcomings, such as, for example: the supplies of ribbon-connected staples must be custom made (generally by the stapler machine manufacturer) for the specific machine, packaged and delivered to the costumer, via the regular commercial channels and therefore such supplies, when available, are unavoidably a great deal more expensive than the conventional staples sold in bulk. The ribbon for interconnecting the staples is expensive and usually constitutes a waste. Further, a certain amount of energy is necessary for the step-by-step shearing the ribbon of the ribbon mounted staple, which results therefore in additional pressurized air consumption. In order to obtain sufficient stapling results there have to be provided, powerful and heavy automatic stapling machines.